This invention relates to a heat developable color photosensitive material capable of forming color images in a heat development and more particularly to a heat developable color photosensitive material capable of obtaining heat developable color diffusion transfer images substantially high in a maximum density.
Photographic methods using the conventional known photosensitive silver halides are superior to the other photographic methods in gradation, image lasting quality and the like, and they have most popularly been put into practice.
In these methods, however, there have been many problems such as that it takes time and labor to process and there is some fear for inflicting an injury upon a person with processing chemicals or a contamination upon a worker and a processing room with the chemicals and further a measure against environmental pollution is to be taken for waste liquids. It has, therefore, been expected to develop such a photosensitive material as is capable of using a photosensitive silver halide and being processed in a dry process.
There have been many proposals for the abovementioned dry process photographic systems. Among them, a heat developable photosensitive material of which developing step can be carried out in a heat process is attracting attention as a photosensitive material capable of answering the abovementioned expectation.
Such heat developable photosensitive materials are described in, for example. Japanese Patent Examined Publication No. 4921/1968 and 4924/1968, wherein the photosensitive materials each comprising an organic silver salt, a silver halide and a reducing agent are disclosed.
Further, some attempts have been tried for improving the abovementioned heat developable photosensitive materials to obtain color images in a variety of processes.
In U.S. Pat. Nos. 3,531,286, 3,761,270, 3,764,328 and the like, for example, there disclose the heat developable color photosensitive materials capable of forming color images in a reaction of the oxidation products of an aromatic primary amine developing agent with couplers.
In Research Disclosure Nos. 15108 and 15127, there disclose the heat developable color photosensitive materials each capable of forming color images in a reaction of the oxidation products of the developing agent comprising a sulfonamidophenol or sulfonamidoaniline derivative with couplers. In the abovementioned processes, however, there is such a problem that color images obtained become turbid. because a reduced silver image and a color image are produced at the same time in an exposed area, after a heat development is completed. To solve the abovementioned problem, there is such a method in which a silver image is removed in a liquid process, or dyes only are transferred to another layer such as an image receiving sheet having an image receiving layer. However, the methods still have such a problem that it is not so easy to distinguish the dyes from unreactants so that the dyes only may be transferred to another layer.
Research Disclosure No. 16966 discloses a heat developable color photosensitive material capable of forming color images in such a manner that an organic imino silver salt having a dye portion is used and the imino groups are set free in exposed areas in a heat development so that a color image may be formed with a solvent on an image receiving layer that serves as a image transfer paper. However, this method still has problems that it is hard to inhibit the dyes in unexposed areas from being set free and a sharp and clear color image may not therefore be obtained.
In Japanese Patent Publication Open to Public Inspection (hereinafter called Japanese Patent O.P.I. Publication) Nos. 105821/1977, 105822/1977 and 50328/1981, U.S. Pat. No. 4,235,957, Research Disclosure Nos. 14448, 15227 and 18137, and the like, there disclose the heat developable color photosensitive materials each capable of forming positive color images in a heat sensitive silver dye bleaching process. In the abovementioned process, however, there are problems that extra processes and photographic component materials are required for superposing sheets each containing an activating agent for accelerating the bleach of dyes, and color images obtained are gradually reduced and bleached with co-existing freed silver or the like, in a long preservation of the images.
U.S. Pat. Nos. 3,180,732, 3,985,565, and 4,022,617, and Research Disclosure No. 12533 each disclose heat developable color photosensitive materials capable of forming color images in utilizing leuco dyes. In the abovementioned processes. however, there are the problems that it is difficult to contain the leuco dyes stably in a photographic photosensitive material and the photosensitive material is gradually colored in preservation.
Japanese Patent O.P.I. Publication No. 179840/1982 discloses a heat developable color photosensitive material capable of forming color images in using a dye releasing assistant and a reducible dye-providing substance capable of releasing a diffusible dye.
Japanese Patent O.P.I. Publication Nos. 186744/1982, 123533/1983, 149046/1983 and 149047/1983, and Japanese Patent Application No. 109293/1983 each disclose heat developable color photosensitive materials each capable of obtaining transferred color images in releasing or forming diffusible dyes through a heat development. The heat developable color photosensitive materials such as those disclosed in the abovementioned patent specifications have such a disadvantage that a maximum density (Dmax) of a transferred image is relatively lower, or a fog (Dmin) thereof is relatively greater.
There have recently been some techniques proposed especially for increasing a maximum density. Namely. Japanese Patent O.P.I. Publication Nos. 57231/1984, 74547/1984, 84236/1984, 180554/1984 and 177550/1984, for example, disclose a variety of matters to serve as a development accelerator.
And, Japanese Patent O.P.I. Publication No. 178457/1984 discloses an aliphatic amide or a formylamide to be used in a method of accelerating the rate of forming a dye image. Every one of the disclosed techniques has the disadvantage that they are still insufficient to obtain a high maximum density or a fog is substantially increased.
Japanese Patent Application 104249/1983 describes a technique that the transferability of dyes may be improved by using a binder, such as gelatin and polyvinyl pyrrolidone, which contains a heat solvent.
Japanese Patent Application No. 169321/1983 describes a technique of improving a heat development and a dye transferability in using gelatin and polyvinyl alcohol to serve as a binder.
Japanese Patent Application No. 223274/1983 describes a multilayer type heat developable color diffusion transfer photosensitive material which is improved in the dye transferability by interposing between two photosensitive layers an interlayer containing a binder containing gelatin and the derivatives thereof in an amount of less than 50% by weight.
Even in the abovementioned techniques, any fully satisfactory dye transferability cannot be obtained. There are, accordingly, demands for the developments of a heat developable color photosensitive material capable of displaying an excellent dye transferability and a high image density.